This invention relates to what is commonly known as silk screen printing. While the term silk screen printing is widely used, materials other than silk may be used to form the screen. For silk screen printing a wood or metal screen frame is needed over which the screen material is stretched. The art work may be produced on the silk screen in a number of different ways. Thus, for example, the art work may be placed on the screen by using oily paint, lithographic crayon or other oil base drawing ink as the screen is stretched tightly in the frame. Primarily, however, the art work is produced with a hydrophobic material. After drying, the art work which is positive, is run over with a water soluble glue or size. This shuts up the mesh holes of the screen material outside of the hydrophobic oil like grease or grease like material. As a consequence, the art work itself does not become coated at these points on the screen materials. After drying of the glue, the oil base coloring material or paint is washed out with gasoline or turpentine so that at these points, the ink will be let through. The frame has to be large enough so that at the edge there is still enough space for the printing ink and for the squeegee. The squeegee is normally made of a handle with a broad cross runner made of wood with a strong rubber strip mounted in it. The mounted rubber strip has been generally trued up by plane grinding. The paper is placed on the screen printing table under the screen and may in some cases be kept in position by a vacuum system. The screen with the art work is then put into position, a thick layer of printing ink is put onto one end of it. The squeegee is then pulled over the screen towards its other end while evenly pushing it against the screen so that a certain amount of ink is forced through the open mesh holes onto the paper. In this way, a great different variety of materials can be printed as for example, metal, wood or glass. The art work may further take the form of paper or film stencils which are adhesively joined to the screen materials. As will be appreciated the strong and solid plane of the machined rubber strip has the purpose of evenly inking or printing and evenly forcing the printing ink through the mesh of the screen material. Therefore, the crucial part of the invention is that the rubber strip of the squeegee is produced with the highest possible degree of exactness in the length-direction and rests completely flatly in its working position on the screen. Furthermore, if the material to be screened is of a material other than flat and planar, it is necessary to make the screen and the squeegee so that its profile follows the contour of the surface to be printed. Thus, for example, if the surface to be printed is convex, it is necessary to use a concave screen material and a concave squeegee.
Squeegee strips consist normally in screen printing of rubber or an elastic plastic. They must be so designed that their edge act directly on the ink in suitable form (blade angle) and brings the screen in proper contact with the surface of the material to be printed, and not only presses the ink into the screen during its movement, but also removes it evenly from the surface of the screen. This requires not only a correct thickness and elasticity of the squeegee strip, but also a suitable design of the profile.